In recent years, efforts have been made to enhance the level of safety in car accidents. With respect to the safety of vehicles, it has been required not only to ensure the safety of occupants in an accident but also to prevent a pedestrian from being fatally damaged when he/she collides with a vehicle.
With respect to devices for protecting a pedestrian who has collided with a vehicle, there is devised a method of reducing the value of an injury suffered by a pedestrian, who collides with a vehicle and falls down on the engine hood (impact received by the pedestrian). Impact a pedestrian receives is reduced; thereby, the pedestrian is prevented from being fatally damaged. In these protective devices, it is important to sense or detect a collision of a pedestrian or the like with a vehicle.
With respect to devices for detecting a collision with a vehicle, there are, for example, methods of assembling a wire, a stress sensor, or an optical fiber to a front bumper. In these methods, a collision is sensed from change in the tension of the wire, an output signal from the stress sensor, attenuation of light passing through the optical fiber, or the like.
However, these devices involve a problem. It is required to install a wire, a stress sensor, or an optical fiber along a front bumper and this incurs the expansion of an installation space or the complication of installation structure. That is, this results in degradation in ease of assembly and increase in assembling cost.
To cope with this problem, there is developed a collision detection apparatus with attention paid to the fact that a side member or a crash box originally equipped in a vehicle is deformed at the time of a collision. This collision detection apparatus is constructed of: a bumper reinforcement so disposed that it is extended in the direction of the width of the vehicle; a side supporting member as a side member or a crash box coupled with the bumper reinforcement and so disposed that it is extended in the direction of the length of the vehicle; and a strain detecting device for detecting strain produced in the side supporting member.
When the side supporting member (crash box) produces strain due to a collision, the collision detection apparatus detects this strain and thereby senses the collision.
However, this collision detection apparatus for detecting or sensing a collision by detecting strain in a side supporting member involves a problem. The side supporting member and the strain detecting device can be displaced from each other and this can lead to a detection error. That is, the accuracy of strain detection is degraded in the collision detection apparatus.